1. Field
The field is fastening devices, including devices that are used to anchor hooks and fasteners in hollow walls, ceilings, and panels comprising one or more layers.
2. Prior-Art Fasteners
Most walls and ceilings of residential and commercial structures have a hollow cavity construction, i.e., there is a hollow space behind the wall. The wall comprises a sheet of material, typically between 1 and 2.54 cm thick, affixed to a suitable frame which includes wood or metal framing members (studs or joists). These are typically spaced on 41 or 61 cm centers. Such sheet material is sold under various trademarks, such as SHEETROCK by United States Gypsum Co., Chicago, and is known generically as drywall, wallboard, plasterboard, and gypsum board. Another less-common wall and ceiling material with similar characteristics is plaster applied over a lath substrate. In the discussion below, the terms wall and ceiling are synonymous.
A variety of fasteners are commercially available for attaching, hanging, or securing objects such as pictures, minors, shelving, cabinetry, towel racks, handrails and other objects to a wall at a location other than over the area where a framing member is located.
Most prior-art anchoring fasteners can be divided into three general types: toggle, expansion, and penetration.